Providers of telecommunications services, such as AT&T, utilize various types of transmission media, including optical fiber cable. As compared to copper cables, optical fiber cables afford greater bandwidth and reduced susceptibility to electromagnetic interference. These advantages of optical fiber cables have prompted telecommunication service providers to employ optical fiber cables whenever possible, especially for trunk applications between facilities.
To protect optical fiber cables against damage, many telecommunications providers bury their optical fiber cables underground. While underground burial protects optical fiber cables from many kinds of damage, burial does not necessarily shield cables from environmental hazards, such as lightning damage. Indeed, optical fiber cables tend to be very susceptible to lightning strikes.
During the spring and summer months, storms occur frequently during which lightning may strike the earth thousands of time. Many lightning strikes often occur near buried optical fiber cables, leading to minor or even major cable damage. Detecting major cable damage, and repairing it can consume many hours. Detecting minor cable damage may be very difficult. As a result, such damage may go undetected. If lightning does strike an optical fiber cable, the lightning will likely travel along a metallic shield or sheath within the cable to a facility where the cable terminates, such as a central office, for example. The receipt of a lightning strike at a piece of equipment within the central office may cause the equipment to fail. Equipment failure due to lightning may lead to a failure of associated alarm reporting systems, making the loss of the equipment difficult to detect, especially at remote facilities that are unmanned.
Thus there is a need for a technique for detecting the presence of a lightning strike on or near an optical fiber cable.